The invention concerns a device and method to produce metal cages for reinforced concrete structures such as beams, pillars or foundations.
Metal cages used for reinforcement purposes in reinforced concrete structures comprise a plurality of longitudinal rods to which stirrups, separated lengthwise, are associated.
It is possible to assemble the cages manually or partly automatically, but in any case it is a long and complex process, particularly to position and distribute the stirrups and the longitudinal rods, since the workers are obliged to make continuous measurements before they can attach them, and there is a high probability of error.
Even when partly automatic machines are used, it is very problematic to position the round pieces in the correct attachment positions, to insert the longitudinal rods inside the perimeter of the stirrups, to move the partly or entirely assembled cages, to position the welding assemblies correctly, and other operations.
Moreover, the variety in the structure of such cages obliges the producer to make a personalized production, almost exclusively to order.
There has been a proposed solution wherein, in a first step, a substantially standardized pre-cage is made, by attaching two auxiliary round pieces outside the stirrups, and in a second step, and in a second zone, the cage is completed with the rods according to specifications.
However, this solution does not solve the problems of positioning and centering the stirrups, of feeding the auxiliary round pieces and of handling the pre-cage/completed cage.
To be more exact, in conventional solutions it is very problematic to insert the round pieces which complete the cage inside the perimeter of the stirrups, once the pre-cage has been completed.
Inserting the round pieces, especially in large-size cages, can require time comparable to the time taken to form the pre-cage, which means there is a risk of injury to the workers, the labor costs are expensive, equipment is needed and there is a risk of damage to the material.
The present Applicant has devised and embodied this invention to overcome these shortcomings and to obtain further advantages.
The invention is set forth and characterized in the main claims, while the dependent claims describe other characteristics of the invention.
The purpose of the invention is to achieve a device suitable to form reinforcement cages comprising at least two longitudinal round pieces able to connect the stirrups to each other so as to constitute a pre-cage; said device is suitable to facilitate the operations to insert the longitudinal rods which complete the cage inside the perimeter of the stirrups once the pre-cage has been completed.
The device according to the invention comprises at least a supporting plane on which the cage or pre-cage is made to advance gradually as it forms.
In a preferential embodiment, there are step-wise feed means included for the longitudinal round pieces to be attached to the stirrups, means to position at least one stirrup at a time between the round pieces in the attachment position and at least a work assembly for at least each one of said longitudinal round pieces.
According to the invention, the rods which according to specifications have to be inserted inside the stirrups which complete the cage are deposited on the supporting plane on which the cage or pre-cage is progressively formed.
The supporting plane has or cooperates with means to keep said rods at least temporarily raised, in order to allow the lower side of the stirrups to pass.
The lifting means are able to allow the free advance of the stirrups without interfering with them, allowing the rods to be progressively inserted inside the stirrups as the cage is gradually formed and as a growing number of stirrups advance on the supporting plane.
Therefore, already when the pre-cage is being formed, the rods which complete the cage are inserted inside the perimeter of the stirrups: this considerably facilitates the subsequent finishing steps.
According to a variant, at the opposite end of the rods from that where the stirrups are introduced, there are means able to define an at least temporary abutment position for the rods.
According to another variant, the position of said abutment means can be regulated according to the length of the rods.
In a first embodiment, the lifting means comprise at least a roller located orthogonal to the axis of advance of the cage along said supporting plane and partly protruding therefrom.
According to this first embodiment, the roller has a plurality of radially arranged paddles on its circumference; the number of the paddles is such that they are always operating on the rods.
In a preferential embodiment, there are six paddles.
The axis of the roller is arranged, with respect to the supporting plane, in such a manner that the paddles protrude partly from said plane for an entity correlated to the desired value by which the rods are lifted.
The paddles of the roller keep the rods raised, allowing the lower side of the stirrups to pass below them; the paddles however do not interfere with the advance of the stirrups since the rollers are made to rotate when the lower side of a relative stirrup enters into contact with the first paddle and makes it rotate.
According to a variant, the means to keep the rods raised for the stirrups to pass comprise two or more movable blades arranged at intervals along the supporting plane, wherein at least a front blade and a rear blade have alternately a respective raised working position and a lowered inactive position.
When a stirrup is approaching the group of blades, the front blade is raised to keep the rods high, while the rear blade is lowered and lets the stirrup pass; then, the rear blade is lifted to lift the rods, while the front blade is lowered to allow the stirrup to pass.
According to a variant, the device also comprises means to make the stirrups in a manner which is functionally and temporally correlated to the progressive formation of the cage on the supporting plane by said work assemblies.
The means to make the stirrups, in a further embodiment, are associated with automatic loading means able to pick up on each occasion one or more prepared stirrups and to put them in said means and between the round pieces advancing step-wise, in a defined attachment position.
The feed means of the round pieces may consist of drawing means with rollers, gripper means with alternate movement, track means, or chains, or other similar or identical systems.
According to one embodiment of the invention, the round pieces arrive from a roll and cooperate with straightening means arranged upstream and/or downstream of the feed means.
According to a further variant, the round pieces are already pre-straightened and of the desired length.
In a first embodiment, for each round piece, there are attachment means able to make the round piece solid with one or more stirrups simultaneously, which stirrups are located on each occasion in the positioning means.
The attachment means, in the preferential embodiment, consist of one or more welding assemblies. In an advantageous embodiment, the welding assembly cooperates with pressure means to position and center the round piece with respect to the relative stirrup in order to improve the effectiveness and hold of the welding.
According to another embodiment, the work assembly also comprises shears means able to cut a relative round piece when the cage, or pre-cage, is substantially complete, or when it is necessary to cut the front part of the cage from the rear part. The shears means therefore also perform the function of emergency shears in the event of a blockage or malfunction.
According to a variant, there are also means able to achieve, on each round piece and in a manner correlated to the feed step, one or more loops in correlation with the position of the stirrup or stirrups and distanced lengthwise.
The loops are aligned lengthwise on at least one round piece and have a convex shape facing outwards; they define seatings in which the stirrups cooperate and are then attached to said round pieces.
According to another feature of this invention, the supporting plane and the work and feed assemblies cooperating with the round pieces have a reciprocal position which can be regulated at least vertically.
In a first embodiment, the supporting plane can be regulated in height in order to define the height at which the round pieces are positioned with respect to the stirrups. In another embodiment, all the work and/or feed assemblies can be regulated together, at least in height, with respect to the supporting plane.
According to another embodiment, each work assembly and/or feed assembly of a relative round piece can be regulated independently so as to define the attachment position of the round piece on the stirrup.